In recent years, wearable devices have been under active development. Since wearable devices are worn on one's body, it is preferable that they have shapes curved along a curved surface of the body or they are curved according to the movement of the body. Therefore, it is preferable that a secondary battery used in a wearable device have flexibility like those for displays and other housings.
Furthermore, the hermeticity of an exterior body of a secondary battery should be high. For example, Patent Document 1 discloses an example of a secondary battery having a laminate exterior body with high hermeticity.